1. Technical Field of the Invention
This invention relates to an apparatus and method for recording holographic image of human subjects safely and in a manner whereby dark eye adaptation of the subject is minimized and to obtain the recording of more lifelike human images.
2. Description of the Prior Art
The recording of images by a holographic process necessarily requires a laser source to generate the object beam and the reference beam. The energy generated by a laser must be of sufficient intensity to record a holographic image on a holographic film plane.
Particularly when the object being recorded is a human subject, the geometries of the object and reference beam paths should be such that any risk that the subject be exposed to laser light be maintained at a minimum. In fact, present laser safety regulations have set the exposure levels based upon what can be safely tolerated by the human eye. (ACGIH (1972), American Conference of Governmental Industrial Hygienists; ANSI (1973), American National Standard for the Safe Use of Lasers).
In holographic applications, the object beam is normally expanded by the use of lenses and then diffused by the use of ground glass screens or the like. If the object beam is not properly expanded or diffused, it may pose a hazard to a human subject. Also, the reference beam, which must be undiffused because it necessarily must have a higher energy level to facilitate recording of a holographic image, also poses a potential threat to human subjects. Various geometries such as an overhead reference beam give partial safety, but do not absolutely safegurard against accidental or deliberate viewing of the reference beam by a human subject.
Another consideration when recording holographic images of human subjects is to obtain the most lifelike reconstruction and clarity of the image. However, at the instant the holographic image is recorded, the room should be generally free of light sources other than the laser light which generates the object beam and the reference beam. When using a pulse laser to record an image, it is generally desirable for the subject to sit in a dark room up until the moment that his image is recorded. However, as is well known, the pupil of the eye varies in diameter in response to the illumination level. Accordingly, the prior art attempts to record holographic images of human subjects under dark room conditions have resulted in reconstructed images whereby the subject's pupils have been unusually large in size which is unlifelike.
Accordingly, it would be desirable to provide an apparatus and method for recording holographic images in human subjects which is both safe and which results in natural and lifelike images being recorded.